Passenger Seat Occupancy Detection

The new passenger seat occupancy detection system introduced on the E89 consists of a seat occupancy pad with integrated capacitor plate. The previous generation occupancy (OC3) detection was realized via the use of pressure sensors attached to the seat cushion.

In the new capacitive sensing passenger occupancy detection system, an electrical field is generated across the capacitor plate and vehicle ground. The seat occupancy mat is connected to an electronic evaluator. The occupancy status is classified based on the evaluation of the electrical field.

A person sitting down on the seat changes the electrical field. The change is registered by the electronic evaluator and the corresponding status is determined. The electronic evaluator sends the status information cyclically to the MRS control unit. Data exchange takes place by means of a hardware link. The seat occupancy detection function monitors the inputs and outputs. Possible fault statuses are stored in the fault code memory of the MRS control unit.

Fig 1: Identifying Capacitive Seat Occupancy Sensor

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: MRS 7 Circuit Diagram

Courtesy of BMW OF NORTH AMERICA, INC.